PEPICO coincidence

PEPICO, see Photoelectron photoion coincidence spectroscopy Peptides... 

Photoionization always produces two species available for analysis the ion and the electron. By measuring both photoelectrons and photoions in coincidence, the kinetic electron may be assigned to its correlated parent ion partner, which may be identified by mass spectrometry. The extension of the photoelectron-photoion-coincidence (PEPICO) technique to the femtosecond time-resolved domain was shown to be very important for studies of dynamics in clusters [131, 132]. In these experiments, a simple yet efficient permanent magnet design magnetic bottle electron spectrometer was used for photoelectron... 

Combination of PES with mass spectrometry in a coincidence system leads to an extremely powerful technique called photoelectron-photoion coincidence (PEPICO) spectroscopy, which renders it possible to examine dissociations of energy-selected molecular ions. 

A typical PEPICO apparatus is shown in Figure 1, where an acceleration region followed by a drift tube is used to determine the ionic species. The coincidence condition is achieved by using electron and ion signals as start and stop inputs, respectively, to a time-to-pulse height converter whose output is sent to a multichannel pulse height analyser. 

Several methods exist that allow the determination of the standard enthalpies of formation of the ionic species. The reader is referred to two recent rigorous and detailed chapters by Lias and Bartmess and Ervin. The vast majority of the experimental data reported here are obtained by means of Fourier transform ion cyclotron resonance spectroscopy (FT ICR), high-pressure mass spectrometry (HPMS), selected ion flow tube (SIFT), and pulsed-field ionization (PFI) techniques, particularly pulsed-field ionization photoelectron photoion coincidence (PFI-PEPICO). All these experimental techniques have been examined quite recently, respectively, by Marshall, Kebarle, B6hme," ° Ng" and Baer. These chapters appear in a single (remarkable) issue of the International Journal of Mass Spectrometry. An excellent independent discussion of the thermochemical data of ions, with a careful survey of these and other experimental methods, is given in Ref. 37. 

From PFI-PE spectroscopy and ion coincidence detection using multi-bunch synchrotron radiation. "From the experimental AfH°n,(C2H4) and PA(C2H4) = 162.98 kcal mol computed at the G2 level. PFI-PEPICO TOE experiments and experimental Affl°n,(g) for the various precursor species. " ... 

Remarkably coincident experimental values for A H° 6) can be obtained from (1) PEPICO studies on tert-butyl iodide " (2) appearance energies for the formation of 6 from isobutane, neopentane and tert-butyl iodide (threshold... 

PFI-PEPICO pulsed field ionization photoelectron-photoion coincidence technique... 

Figure 5.15 The experimental arrangement of a photoelectron photoion coincidence (PEPICO) set-up. Electron energy analysis is accomplished by an electrostatic energy analyzer, by electron TOP when the light source is pulsed, or by angular discrimination against energetic electrons. Taken with permission from Baer (1986).

The translational PED for the I-atom loss from CH3I+ is a classic example of a reaction with statistical PEDs. Figure 9.10 shows the translational PEDs at three excess energies as measured by photoelectron photoion coincidence (PEPICO) using a room-... 

Figure 10.2 Photoelectron photoion coincidence (PEPICO) time of flight spectra of methanol and methylchloride clusters. Sharp peaks are observed if a cluster ionizes without dissociation. The broad peaks are a result of kinetic energy release in dissociative ionization. Taken with permission from Booze and Baer (1992).

Photoionization has a number of advantages over electron impact ionization, such as greater sensitivity and thresholds that are easier to define. In coincidence photoelectron techniques (e.g., photoelectron photoion coincidence spectroscopy, PEPICO, and threshold photoelectron photoion coincidence spectroscopy, TPEPICO), the photoelectron and the photoion formed in the ionization process are detected simultaneously, thus providing information on the nature and energies of the ionized products. ... 

PEPICO Form of photoionization mass spectrometry in which ions produced by photoionization are detected in coincidence with the accompanying energy-seiected photoeiectrons. 

The validity of the statistical approximation in QET-RRKM-phase-space theories has been tested extensively both experimentally and theoretically. Some of the most incisive tests of statistical theory have been performed with energy-selected ions, prepared as described previously, using methods such as photoelectron-photoion coincidence (PEPICO). Particularly incisive tests of these statistical models have been performed on isomeric C4Hg systems by Baer and Bowers and their co-workers and on C4H by Bowers and collaborators. The latter study provided validation of an important variant of statistical theory called the transition state switching model. 

Photoelectron-Photoion Coincidence Methods in Mass Spectrometry (PEPICO)... 

Multiphoton Excitation in Mass Spectrometry Negative Ion Mass Spectrometry, Methods Neutralization-Reionization in Mass Spectrometry Photoelectron-Photoion Coincidence Methods in Mass Spectrometry (PEPICO)... 

See also Environmental Applications of Eiectronic Spectroscopy Fragmentation in Mass Spectrometry ion Dissociation Kinetics, Mass Spectrometry ion Energetics in Mass Spectrometry Laser Appiications in Eiectronic Spectroscopy Metastabie ions Muitipho-ton Spectroscopy, Appiications Negative ion Mass Spectrometry, Methods Photoeiectron-Photoion Coincidence Methods in Mass Spectrometry (PEPiCO) Photoionization and Photodissociation Methods in Mass Spectrometry Spectroscopy of ions Time of Flight Mass Spectrometers. 

PHOTOELECTRON-PHOTOION COINCIDENCE METHODS IN MASS SPECTROMETRY (PEPICO) 1831... 

Photoelectron-photoion coincidence (PEPICO) is a method for energy selecting ions and studying their... 

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